This application addresses NIH's broad Challenge Area (06) Enabling Technologies and specific Challenge Topic, 06-DC-103* Understanding the Neural Mechanisms Responsible for Tinnitus. The proposed work investigates changes that occur in the auditory part of the brain after damage to the cochlea, particularly changes that may underlie the sensation of tinnitus or phantom sound. Animals will be given acoustic trauma over a range of severities from mild to moderate. We expect that this will produce animals with and without tinnitus, based on a behavioral test of the animals'phantom sound perception. We will record from neurons in a part of the brain that seems to be involved in tinnitus and characterize abnormalities in the electrical activity of its neurons, specifically abnormal spontaneous activity, spontaneous bursting activity, elevated randomness in their spontaneous discharge rates, and abnormal synchrony among neurons. The extent of various abnormalities will be related to the presence or absence of tinnitus to provide evidence for the specific abnormalities underlying tinnitus. Tinnitus is a condition affecting a large number of persons. Although it often accompanies hearing loss, it does not necessarily do so and may occur with little hearing impairment. The phantom sounds of tinnitus range from a minor annoyance to a debilitating problem. Attempts to ameliorate tinnitus are hampered by the lack of a clear idea of the nature of the underlying pathophysiology of tinnitus production. PUBLIC HEALTH RELEVANCE: The goal of this work is to identify the aspects of abnormal electrical activity of neurons that are most closely correlated with one form of tinnitus, which is tinnitus following acoustic trauma. The outcome of these studies is expected to aid in designing interventions to reduce tinnitus.